Hydrocarbon conversion



Jan E. H. HYDHOCARBON CONVERSION Filed Sept. 8, 1959 Patented Jan. 1 3,1942.

HYDROCARBON CONVERSION Edwin H. McGrew, Chicago, Ill., assigner toUniversal Oil Products Company, Chicago, El., a corporation of DelawareApplication september 8, i939, serial No. 293,895

5 Claims.

This invention relates to the production of a motor gasoline ofrelatively low olefin content, high octane rating, and relatively lowpotential gum content, which due to its relatively high degree ofsaturation, is useful as aviation gas-' crude and reflux condensate,thermal reforming.

treatment of a relatively light hydrocarbon oil,

such as, for example, gasoline, naphtha, or.

kerosene, high temperature catalytic cracking treatment of anintermediate oil,such as, for example, kerosene or gas oil, commonfractionation of the conversion products from the thermal cracking andreforming treatments, and the high tially atmospheric to 200 pounds ormore per square inch in the presence of a catalyst of essentially thesame composition as that employed in the high temperature catalyticcracking treatment and the reaction is essentially that of hydrogentransfer.

It has been found that when mixtures of olefin-containing gasolinesproduced by either temperature catalytic cracking treatment and,

low temperature catalytic conversion treatment of the distillate andlight reflux condensate.

formed and separated therein.

The term thermal cracking treatment as used throughout the specificationand claims refers to the conversion of -heavxr hydrocarbons into lighterhydrocarbons by heat and pressure, and in all instances involves thescission of carbon to carbon bonds. The term thermal reforming treatmenton the other hand, refers to the treatment of relatively lighthydrocarbons to im- ,prove their octane rating and may involve thescission of carbon to carbon bonds, the scission of carbon to hydrogenbonds, cyclization and many other reactions of lesser importance. Theterm high temperature catalytic cracking treatment refers to thetreatment of hydrocarbon oils in the presence of catalytcally activemassesat temperatures ranging, for example, from 800 to 1200 F. and atpressures varying from substantially atmospheric to 200 pounds or moreper square inch to effect substantial conversion to l gasoline boilingrange hydrocarbons, and ordinarily involves the scission of carbon .tocarbonl non-catalytic or catalytic methods and a relatively heavyhydrocarbon oil, such as intermediate conversion products from anon-catalytic cracking treatment or from a once-through catalyticcracking treatment, are subjected to contact with a catalyst essentiallythe same composition asthat employed in the catalytic cracking treatmentbut at lower space velocities and lower temperatures, a substantiallysaturated.

gasoline product is obtained. Whereas, inhigh temperature catalyticcracking treatments temperatures of the order of 800 to 1200 F. areemployed with pressures of from substantially atmospheric to 200 poundsor more per square inch with space velocities of from 2 to 6 volumes ofhydrocarbon material per volume of catalyst per hour, in the lowtemperature' treatment temperatures of the order of 500 to 900 F.A areemployed with pressures of from substantially atmospheric to 200 poundsor more per square inch and with space velocities of from .5 to 2.

'I'he hydrogen content of the intermediate conversion products from anon-catalytic cracking treatment is ordinarily high as compared to vthatof the intermediate conversion products from a catalytic crackingtreatment when `recycle operation is employed in both cases, andtherefore the intermediate conversion products from the non-catalyticcracking treatment are preferred as the hydrogen donor. On the otherhand, the hydrogen content of the intermediate conversion productsformed in a once-through catalytic cracking treatment is also high, andthis material may be employed as the hydrogen donor in the lowtemperature catalytic conversion treatment.

The reaction involved in low temperature catalytic conversion isessentially one of transferring hydrogen from the heavier hydrocarbonsto the lighter olefinic hydrocarbons to convert the latter to parainichydrocarbons, although cracking, cyclizatlon, and isomerizationreactions may also be involved. It is believed that in low temperaturecatalytic conversion treatment saturated hydrocarbons and particularlythe naphthenic hydrocarbons of the recycle oil actas hy?,

the gasoline, while the oleflnic hydrocarbons become saturated to formparaflinic hydrocarbons and the naphthenic hydrocarbons are converted toaromatic hydrocarbons., Various other reactions, such as, for example,dehydrogenation and cyclization of an aliphatic hydrocarbon to form anaromatic hydrocarbon with the formation of two or three molecules ofhydrogen which attach to the unsaturated oleiinic hydrocarbons may alsotake place. However, since the invention is concerned primarily with aprocess in which the various reactions may be conducted, furtherdiscussion with regard to the chemical reactions which may possibly beinvolved is unnecessary for a full understanding of the invention whichis to be vdescribed later in more detail.

In one specific embodiment the invention comprises subjecting combinedfeed comprising heavy reflux condensate, formed as hereinafterdescribed, and a relatively heavy hydrocarbon oil to thermal crackingtreatment in a heating coil and communicating reaction chamber,concurrently therewith subjecting a relatively light hydrocarbon oil tothermal reforming treatment, simultaneously in another step subjectingan intermediate oil to high-temperature catalytic cracking treatment ina heating coil and communicating high temperature catalytic reactor,commingling the conversion products from the three treatments andintroducing the mixture to a vaporizing and separating chamber toseparate a non-vaporous liquid residue from the vaporous conversionproducts, recovering the former, fractionating said vaporous conversionproducts to form light and heavy reflux condensate and to separatefractionated vapors boiling in the range of gasoline, subjecting theheavy reilux condensate to thermal cracking treatment, as previouslydescribed, cooling and condensing said' fractionated vapors, separatingthe resulting distillate and gas and recovering the latter, comminglingsaid distillate with the light reflux condensate, heating the mixtureand subjecting the heated oil to contact with a cracking catalyst in thelow temperature catalytic reactor, fractionating the conversion productsfrom said low temperature catalytic reactor to form reflux condensateand to separate vapors boiling in the range of gasoline, subjecting saidreflux condensate to thermal cracking treatment in commingled state withsaid heavy reflux condensate, formed as previously described, coolingaand condensing said vapors and recovering the resulting distillate andgas as products of the process.

The accompanying diagrammatic drawing shows in conventional sideelevation one specific form of the apparatus in which the object of theinvention may be accomplished. It is to be understood, however, that theinvention is not limited to the use of the specific form of apparatusherein shown and that various departures may be made therefrom withoutdeviating from the spirit of the invention.

Referring now to the drawing, a relatively heavy hydrocarbon oil, suchas, for example, a topped or reduced crude oil is introduced throughline I and valve 2 to pump 3, which discharges through line 4 and valve5, said heavy oil commingling with heavy reflux condensate, formed ashereinafter described, and the combined feed introduced to heating coil6. The oil in passing through heating coil 6 is raised to the desiredcracking temperature which may range, for example, from 850 to 1000 F.and is maintained at this temperature for a sufcient period of time toeffect substantial thermal cracking thereof, heat being supplied fromfurnace 1. The hot conversion products leaving heating coil 6 at asuperatmospheric pressure ranging, for example, from 200 to 600 poundsor more per square inch, are directed through line 8 and valve 9 intoreaction chamber I0 wherein they are subjected to prolonged conversionat the cracking temperature. Reaction chamber I0 is preferablyoperatedat a superatmospheric pressure substantially the same as that employedon the outlet of heating coil 6 and is preferable insulated to reduceradiation losses therefrom, although no insulation is shown in thedrawing. The vaporous and liquid conversion products leaving chamber I0are directed through line II and valve I2 into vaporizing and separatingchamber I3 for treatment as hereinafter described.

In addition to the thermal cracking treatment of a heavy hydrocarbonoil, the invention also proposes to thermally reform a relatively lighthydrocarbon oil, such as gasoline, naphtha,'or kerosene, or any mixturethereof, and to catalytically crack an intermediate oil at relativelyhigh temperatures to produce more valuable products than either of thetwo last mentioned charging stocks. The use of either of theseoperations is optional and may depend upon the amount of high octanesubstantially saturated motor fuel desired, which may vary for eachspecific case. In accordance with the objects of the invention, however,since both thermal reforming and high temperature catalytic crackingyield a gasoline product rich in olefinic hydrocarbons and since theobjective in all cases is to treat each hydrocarbon oil under theoptimum conditions for the production of motor fuel, such operations maybe conveniently employed in combination with a thermal crackingtreatment and the gasolines produced in al1 cases subjected to lowtemperature catalytic conversion treatment to produce a substantiallysaturated motor fuel.

Thermal reforming treatment, in the case here illustrated, may beaccomplished by introducing a relatively light hydrocarbon oil, such as,for example, gasoline, naphtha, or kerosene, or any mixture thereof,through line I4 and valve I5 to pump I 6, which dischargesI through linell and valve i8 into heating coil I9. The oil in passing through heatingcoil I9 is subjected to thermal reforming treatment at a temperatureranging, for example, from 950 to 1050 F. by means of heat supplied fromfurnace 20. The conversion products leaving heating coil I9 at apressure ranging, for example, from 500 to 1200 pounds per square inchare directed through line 2l and valve 22 into line Il where theycommingle with the vaporous and liquid conversion products from reactionchamber I0.

The high temperature catalytic cracking treatment may be accomplished byintroducing an intermediate oil, such as kerosene, or gas-oil, or anymixture thereof, through line 23 and valve 24 to pump 25, whichdischarges through line 26 and valve 2l into heating coil 28. The oil inpassing through heating coil 28 is substantially completely vaporizedand raised to the desired temperature, which may range, for example,from 800 to 1200 F. without substantial pyrolytic cracking thereof bymeans of heat supplied from furnace 29. The heated vapors leavingheating coil 28 at a pressure ranging, for example, from substantiallyatmospheric to 200 pounds or more per square inch are directed throughline 30 and ,ferred to above.

be prepared by precipitating silica from a solution disposed thereinwhile maintaining the hydrocarbon vapors at substantially the sametemperature as that employed on the outlet of the heating coil by meansof heat supplied from an external source.

The preferred cracking catalysts for use in the present process consistsin general of a precipitated alumina hydrogel and/or zirconia hydrogelcomposited with silica hydrogel, the gel composite being washed, dried,formed into particles and calcined to produce a catalytic mass. It isnot intended, however, that the process should be limited to theseparticular catalysts, for other catalysts, such as, for example, thehydrosilicates of alumina, acid treated clays, and the like, may be usedwithin the broad scope of. the invention,

In the following specification and claims the terms silica, alumina,silica-zirconia, and silicaalumina-zirconia masses are used in the broadsense to designate the synthetic composites re- The preferred catalystsmay as a hydrogel within or upon'which the alumina and/or zirconia. aredeposited also by precipitaactors are segregated from the balance forthe purpose of reactivation. y

Although the reactor described above constitutes the preferred type ofreactor, it is not intended that the invention should be limited in thisrespect, for various other types of reactors, known to those in the art,may be substituted therefor without departing from the broad scope ofthe invention.

The conversion products leave reactor 32 by way of line 33 and aportion'or all are directed the conversion products from heating coil I9in line -I I for treatment as hereinafter described.

Vaporizing and separating chamber i3 is preferably operated at a reducedpressure relative to that employed in either of the three conversiontreatments or at substantially the same pressure tion as hydrogels. Thesilica hydrogel may coni veniently be prepared by acidifying an aqueoussolution of sodium silicate by the addition of a 5 required amount ofhydrochloric acid. After precipitating, the silica gel is preferablywashed until substantially free-from alkali metal salts. The Washedsilica hydrogel is then suspended in a solution of alumina and/orzirconium salts and an alkaline precipitant, such as ammonium hydroxide,lammonium carbonate or ammonium sulfide added to the solution toprecipitateA which may be ground and pelleted or sized to" produceparticles of catalyst after which the catalyst particles are calcined ata temperature in the approximate range of 1000 to 1500 F. Various otherprocedures, such as, for example,

vco-precipitation of the hydrated gels may be eml ployed, when desired,to produce the preferred catalyst.

Reactor 32 is preferably of the type which employs a plurality ofrelatively small diameter reactor tubes containing the desired catalyst,the tubes being confined within an enclosed zone tov which heat from anexternal source may be sup- The vapors introduced to fractlonator di aresubgasoline.

plied for the purpose of maintaining the ref means, not shown, may beemployed for reactivat` ing the catalyst disposed within the variousreactors during the period those particular reas that lemployed in thehigh temperature catalytic cracking treatment in reactor 32 when lowpressures are employed therein, and it may range,

for example, from 25 to 250 pounds or more per square inch. The liquidconversion-products introduced in commingled state withthe vaporousconversion products in chamber I3 are subjected to substantial furthervaporization therein to form a non-vaporous liquid residue which is4withdrawn from chamber I3 by way of line 3l` and valve 38, cooled andsubjected to any dejected to fractionation therein to form light andheavy reflux condensate and to separate fractionated vapors which may,comprise gasoline boiling range hydrocarbons or may, when desired,include hydrocarbons boiling above the range of The heavy refluxcondensate is directed through line d2 and valve B3 to pump da, whichdischarges through line d5 and valve 66 into line d where said heavyreflux condensate commingles with the heavy oil to form combined feedand said combined feed thereafter subjected to thermal crackingtreatment, as` previously described. f

Fractionated vapors separated inv fractionator il are directed from theupper portion thereof through line 41 and valve 48 to cooling and confdensation in condenser '59. The distillate in condenser 39, togetherwith undissolved and uncondensed gases, is directed through line 50 andvalve 5I into receiver 52 wherein said distillate is separatedA from theundissolved and uncondensed gases, the latter being withdrawn fromreceiver 52 by way of vline 53 and valve 53 and recovered or subjectedto any desired further treatment. A portion of the distillate collectedand separate in receiver 52 may be returned to the upper portion of'fractionator 5I by well known means, not shown, as a refluxing andcooling medium. A portion or all of the remaining distillate in receiver52 may be withdrawn therefrom by Way of line 55 and valve 56andrecovered as a product of the process. Preferably, however, theremaining lboiling range hydrocarbons.

distillate in receiver 52 is directed through line 5l and valve 58 topump 59, which discharges through line 60 and valve 6l into line 65 fortreatment as hereinafter described.

Light reflux condensate from fractionator il is directed through line 62and valve 63 to pump 513, which discharges through line 65 and valve 66and said light reflux condensate commingled with the distillate removedfrom receiver 52, as previously described, the mixture thereafter beingsupplied to heating coil 61.

The mixture of oil introduced to heating coil 61 is raised to atemperature in the range of 500 to 900 F. without substantial pyrolyticcracking thereof by means of heat supplied from furnace 69. The heatedoil leaving heating coil 61 at a pressure ranging, for example, fromsubstantially l atmospheric to 200 pounds or more per square inch isdirected through line E9 and valve 19 into reactor 1| where it issubjected to contact with a cracking catalyst while maintaining the oilat substantially the same temperature as that employed on the outlet ofheating coil 61. The catalyst employed in reactor 1l may be of the samecomposition as that employed and described in connection with reactor32. The low and high temperature catalytic conversion reactions diieressentially with respect to temperature and contact times employed, thereaction in reactor 32 being carried out at a'relatively hightemperature and short contact time, whereas the reaction in reactor 1lis carried out at a lower temperature and at a longer contact time.Reactors 32 and 1| may be essentially of the same design, however, aswas previously .I

mentioned, various other types of reactors may be employed to accomplishthe desired results.

The conversion products leaving reactor 1I are directed through line 12and valve 13 into fractionator 14 which is maintained at substantiallythe same or at a reduced pressure vrelative to that employed on theoutlet of reactorY 1I. The conversion products introduced tofractionator 14 are subjected to fractionation therein to form refluxcondensate and to separate the gasoline Reflux condensate formed infractionator 14, which in this stage of the process containsy relativelylarge amounts of aromatic hydrocarbons, is preferably subjected tothermal cracking treatment and this may be accomplished by directing thesame through line 15 and valve 16 to pump 11, which discharges throughline 18 and valve 19 into line 45 where said reflux condensatecommingles with the heavy reflux condensate fromfractionator 4l, themixture thereafter being subjected to the same treatment as thatperformed on the heavy reflux condensate, as previously described.

Fractionated vapors fromfractionator 14 are directed through line 80 andvalve 8l to cooling and condensation in condenser 82. Distillate,together with undissolved and uncondensed gas- :es in condenser 82, isdirected through line 83 and valve 84 to collection and separation inreceiver 85. Normally gaseous hydrocarbons collected and separated inreceiver 85 are directed from the upper portion thereof through line 8Gand valve 81 to storage or to any desired further treatment. A portionof the distillate collected in the lower portion of receiver 85 may bereturned to the upper portion of fractionator 14 by well known means,not shown, as a refluxing and cooling medium therein. The balance of thedistillate collected in receiver 85 is removed therefrom by way of line88 and valve 89 and recovered as a product of the process.

In carrying out one specic operation of the process illustrated andabove described, the conditions employedand results obtained wereapproximately as follows:

A A. P. I. gravity mid-continent yreduced crude oil was commingled withheavy reflux condensate, formed as hereinafter described, and themixture subjected to thermal cracking treatment in the heating coil andcommunicating reaction chamber at a temperature of 930 F. and under asuperatmospheric pressure of 300 pounds per square inch.

AIn another step of the process a 53 A. P. I. gravity straight-rungasoline fraction was subjected to thermal reforming treatment in aheating coil at a temperature of 1010 F. and under a superatmosphericpressure of 750 pounds per square inch.

In another step of the process a 35 A. P. I. gravity straight-rungas-oil fraction was vaporized and heated to a temperature of 950 F. andthe resulting vapors subjected to contact with a silicaalumina-zirconiacatalyst under a superatmospheric pressure of approximately 60 poundsper square inch while maintaining the vapors in the catalytic zone at acracking temperature.

The conversion products from the thermal cracking and reformingtreatments and the catalytic cracking treatment were commingled and themixture introduced to a vaporizing and separating chamber maintainedunder a superatmospheric pressure of 50 pounds per square inch. Theliquid conversion products introduced to the vaporizing and separatingchamber were subjected to substantial further vaporization to form anon-vaporous liquid residue and the latter, corresponding toapproximately 25.3% of the total charge, recovered as a product of theprocess.

The vapors from the vaporizing and separating chamber were fractionatedto form light and heavy reflux condensates and to separate vaporsboiling below 400 F. The heavy reflux condensate was subjected toconversion, as previously described. The fractionated vapors weresubjected to cooling and condensation and the resulting distillate andgas collected and separated.

The 400 end point distillate recovered was commingled with the lightreux condensate, the mixture heated to a temperature of 750 F. andthereafter subjected to contact with a silica-alumina-zirconia catalystat' a pressure of approximately pounds per square inch while maintainingthe temperature of the materials undergoingconversion at substantiallythat at which they were discharged from the heating coil. The conversionproducts from the low temperature catalytic treatment were fractionatedto form reflux condensate, which was supplied to the thermal crackingtreatment, and to separate fractionated vapors boiling below 300 F.which were cooled, condensed, and recovered as a product of the process.

The above described operation, based on a total feed, distributedapproximately as follows:

44% reduced crude, 22% straight-run gasoline, and 34% gas-oil resultedin a yield of approximately 63.5% of 300 end point gasoline having anoctane number of 74 and a bromine number of 9. With the addition of 6cc. of tetraethyl lead the octane rating was raised to 96. In addition,normally gaseous hydrocarbons were obtained, corresponding toapproximately 100% minus the yield of gasoline and liquid residue, whichcontained a high percentage of polymerizable oleiins.v

I claim as my invention:

v1. The process of converting hydrocarbons, which comprises subjectingcombined feed comprising a relatively heavy hydrocarbon oil and refluxcondensates, formed as hereinafter described, to thermal crackingtreatment, concurrently therewith subjecting a relatively lighthydrocarbon oil to thermal reforming treatment and an intermediate oilto high temperature catalytic cracking treatment, commingling theconversion products from said thermal cracking and reforming treatmentsand from said high temperature catalytic cracking treatment, supplyingthe mixture to a vaporizing and separating zone to separate non-vaporousliquid residue'which is recovered as a product of the process from thevaporous conversion products, fractionating said vaporous conversionproducts to form light and heavy reflux condensate and to separatevapors boiling in the range of gasoline, supplying said heavy refluxcondensate to treatment as aforesaid, cooling and condensing saidvaporsand recovering the resulting distillate and gas, commingling saiddistillate with the light refluxcondensate and subjecting the mixture tolow temperature catalytic treatment, fractionating the conversionproducts from said low temperature catalytic treatment to form refluxcondensate and to separate fractionated, vapors, supplying said refluxcondensate to said thermal cracking treatucts of the process. l

2. The process of. converting hydrocarbons,

which comprises subjecting combined feed comprising a relatively heavy`hydrocarbon oil and reflux condensates, formed as4 hereinafter de-`vscribed, to thermal cracking treatment, concurrently therewithsubjecting a relatively light hydrocarbon .oil to thermal reformingtreatment and an intermediate oil to high temperature catalytic crackingtreatment, commingling the conversion products from said thermalcracking treatment and said thermal reforming treatments and supplyingthe mixture toa vaporizing and separating chamber to separate a non-va-`the mixture to low temperature catalytic treatmen-t, fractionating theconversion products from said low temperature catalytic treatment toform reflux and to separate fractionatedvapors. 'supplying said reuxcondensate to said thermal cracking treatment for treatment as`aforesaid, cooling and condensing said fractionated vapors andrecovering the resulting distillate and gas as products of the process.3. The5 process of converting hydrocarbons, which comprises subjectingcombined feed comreflux condensates, formed as hereinafter described, tothermal cracking treatment, concurrently therewith subjecting arelatively light hydrocarbon oil to thermal reforming treatment and anintermediate oil to high temperature catalytic cracking treatment in thepresence of a silicaalumina catalyst, commingling the conversionproducts from said thermal cracking and reforming treatments and fromsaid high temperature catalytic cracking treatment, supplying themixture-to a vaporizing and separating zone to separate non-vaporousliquid residue which is recovered as a product of the process from thevaporous conversion products, fractionating saidl vaporous conversionproducts to form light and heavy reflux condensate and to separatevapors boiling in the range of gasoline, supplying said -heavy reuxcondensate to said thermal cracking ment in the presence of a catalystof `essentially I the same composition as hereinbefore set forth,

., fractionating the/conversion products from said lowtemperaturecatalytic treatment to form re-i flux condensate and toseparate fractionated vapors, supplying said reux condensate to saidthermal cracking treatment for treatment as aforesaid, cooling andcondensing said fractionated vaporsfand recovering the resultingdistillate and gas as products of the process.-

4. The process of converting hydrocarbons, which comprises subjectingcombined feed comprising a relatively heavy hydrocarbon oil and refluxcondensates, formed as hereinafter described, to thermal crackingtreatment at a temperature of from 850 to 1000" F. and underasuperatmospheric pressure of from 200 to 600 pounds per square inch,concurrently therewith subjecting a relatively light hydrocarbon Oil tothermal reforming treatment at atemperature of from 950 to 1050 F. andat a pressure of from 50 to 200 pounds per square inch, and anintermediate oil to high temperature catalytic cracking treatment in'the presencel of a silica-zirconia catalyst at a temperature of from800 to 12009 F. and under a pressure of from substantially atmosphericto 200 pounds per square inch, commingling the conversion products ,fromsaid 'thermal cracking and reforming treatments and from said hightemperature catalytic cracking treatment, supplying the mixture to avaporizing and separating zone to separate non-vaporous liquid residuewhich is recovered as a product of the process from the vheavy refluxcondensate to said thermal cracking treatment for treatment asaforesaid,cool ing and condensing said vapors and recovering theresulting distillate and gas, commingling said distillate with the lightreflux condensate and subjecting the mixture to low temperature catavlytic treatment inthe presence of a catalyst of es- ,prisinga relativelyheavy hydrocarbon oil and sentially the same composition as thathereinbefore set forth at a temperature offrom 500 to 900 F. and at apressure of from substantially atmospheric to 200 pounds per squareinch, fractionating the conversion products from said low temperaturecatalytic treatment to form reux condensate and to separate fractionatedvapors, supplying said reflux condensate to said thermal crackingtreatment for treatment as aforesaid, cooling and condensing saidfractionated vapors and recovering the resulting distillate and gas asproducts of the process.

5. The process of converting hydrocarbons, which comprises subjectingcombined feed cornprising a relatively heavy hydrocarbon oil and refluxcondensates, formed as hereinafter described, to thermal crackingtreatment at a temperature of from 850 to 1000 F. and under asuperatmospheric pressure of from 200 to 600 pounds per squareinch,concurrently therewith subjecting a relatively light hydrocarbon oil tothermal reforming treatment at a temperature of from 950 to 1050 F. andat a pressure of from 50 to 200 pounds per square inch. and anintermediate oil to high temperature catalytic cracking treatment in thepresence of a catalyst consisting essentially of silica composited withalumina and zirconia, at a temperature of from 800 to l200 F. and at apressure of from substantially atmospheric to 200 pounds per squareinch, commingling the conversion products from said thermal cracking andreforming treatments and from said high temperature catalytic crackingtreatment, supplying the mixture to a vaporizing and separating zone toseparate non-vaporous liquid residue which is recovered as a product ofthe process from the vaporous conversion products, fractionating saidvaporous conversion products to form light and heavy reflux condensateand to separate vapors boiling in the range of gasoline, supplying saidheavy reilux condensate to said thermal cracking treatment for treatmentas aforesaid, cooling and condensing said vapors and recovering theresulting distillate and gas, commingling said distillate with the lightreiiuX condensate and subjecting the mixture to low temperaturecatalytic treatment in the presence of a catalyst of essentially thesame composition as that hereinbefore set forth at a temperature of from500 to 900 F. and at a pressure of from substantially atmospheric to 200pounds per square inch, fractionating the conversion products from saidlow temperature catalytic treatment, to form reflux condensate and toseparate fractionated vapors, supplying said reflux condensate to saidthermal cracking treatment for treatment as aforesaid, cooling andcondensing said fractionated vapors and recovering the resultingdistillate and gas as products of the process.

EDWIN H. MCGREW.

